Why 69xx kHz?

[OgreVorbis]

So I'm new to this forum, but not to pirate radio in general. I pirated before on 1710khz, but the antenna construction is hard and I never seemed to get out very far (plus the ground conductivity where I am is really bad).

Anyway, I want to try pirating on HF and I'm wondering why most people use 69xx khz because for me it would be much easier to make an antenna for around 10-15 MHz. Does anybody listen for pirates around those frequencies? Do they get out as far?

See the graph on this site: http://www.voacap.com/antennas/squeezing-decibels-out-of-dipole/

You can see that if I created an antenna for 10-15, it is very doable to get the peak gain out of the antenna based on the distance from ground. However, if I were to use 69xx, it would be very hard for me to get more than 40ft from the ground and so not much gain...

So would pirating around 10-15 be better?

[redhat]

It depends of who you ask, but the general consensus (in my view anyway) is that it provides a good balance of day and night propagation, particularly at shorter distances.  This allows ops to reach audiences close by during daylight hours via NVIS propagation, and longer distances at night via skywave.  It also has the added benefit of being close enough to the 40 meter ham band to allow commercially produced equipment to be used there.  Although antennas for this area are larger than those used at higher frequencies, propagation via NVIS during daylight hours is more reliable than the higher frequencies.  Higher frequencies also pose difficulties at night for DX, as just about anywhere on the continent would be in the skip zone, and very good propagation conditions are required to reach distant audiences at the power level most pirates have at their disposal.

In all fairness, there have been a few ops running just under the 20 meter ham bands, but usually during daylight hours, which is risky in my judgement.

Location plays into this alot as well.  East coasters rely on NVIS to reach close in targets, and a dipole or inverted V are good antennas for this application.

As always, YMMV...

+-RH

[ChrisSmolinski]

Redhat's summary of the technical reasons for the 69xx band being used are excellent. The only other points I would add are historical - pirate operations in the 80s often occurred in the 74xx range, just above the 41 meter shortwave band (and the 40 meter ham band as well of course). This lasted for quite a few years, until a variety of factors (mostly the 41 meter band expanding up into that region) pushed operations back down to below 40 meters, first on 6955 kHz. That was the hot spot for a while, until interference from a SWBC station (from Chile, I think?) caused enough QRM that operators moved down to 6925, where we are today. Plus of course all the adjacent frequencies being used, 6930 to 6970 in 5 kHz steps. 6850, 6875, and 6900 (plus or minus the crystal tolerance) also are fairly popular today.  Between 6900 and 6920 seems to be a sort of a no mans land - probably avoided due to MARS operations on 6903 and 6913. Ironically, 68xx used to be somewhat popular back in the 80s, I have a QSL from Voice Of The Voyager from 6840.

And of course WRMI has now taken up residence 24/7 on 6915. Or should I say had? Checking my recordings for yesterday, I do not see them on 6915. Not sure if they have moved, or just really poor propagation.  Anyway, I find/found them less of a nuisance than I thought I would as a listener, and more useful as a propagation beacon. Update: I just fired up the SDR this morning, and hear Bro Stair on 6855, so perhaps that is where WRMI moved to?  Hmm. They just went QRT at 1406.  Very strange. OK, back again.
 
Another reason activity has not moved far outside the 69xx band is that is where the listeners are looking. With so many running SDRs and waterfalls, we can spot signals anywhere in the 6800-7000 range as soon as they sign on, and log them. But unless the op lets us know, we generally completely miss transmissions on 10 or 13 MHz, or elsewhere. Several operators have mentioned to me that they have operated on 11 MHz many times, and not gotten a single report. There have been a few attempts to use 3 MHz (several months ago there were quite a few transmissions there), mostly to get around the low foF2 values at night, when 43 meters is completely closed for anyone within a thousand miles of the transmitter site. But in addition to people not checking there, you've got high noise levels (not as bad in the winter as summer), and I imagine antenna problems, both for the transmitter and receiver. Not everyone has an efficient antenna for 90 meters.

One other thing I will throw out - we are at what is actually a historic high period of SW pirate radio activity right now. Amazingly, unbelievably, high. This is probably causing a lot of the activity on frequencies other than 6925, since everyone can't transmit at once on the same frequency. I've often noted 3, and occasionally 4, 5, sometimes even 6 stations on at the same time. That was unimaginable in the 80s and 90s. If you want to talk about the "good old days of shortwave pirate radio", I would say they are right now. There is more to listen to now than at any other time. Ever.

[MDK2]

Adding to what Chris said... Speaking as a complete noob, having owned a real SW receiver for about 3 months now (initially interested in getting numbers stations but finding that pirates are much more plentiful to hear, and easily with the very basic two receivers and longwire I'm using at the moment - no SDR and fancy waterfalls to help find things to listen to), knowing that I can just scroll through that band, either in AM or USB, and sometimes find something without waiting for someone to post something here is very, very satisfying. If you go to a different band, at the very least you would have to announce it somewhere ahead of time (and they do have a subcategory under PIRATE here for that purpose) in order for someone like me to know that there's something worth finding in those bands. I don't go scrolling through 10-11MHz very often because aside from the VOLMET at 10051 kHZ that whole band is something of a dead zone for me. (Doubtless there's interesting stuff there that I don't know how to find, or can't receive with what I have.)

Anyway, I haven't seen the much more veteran commenters address this point, but isn't 43m something of a dead zone, regulation-wise? (WMRI at 6915 notwithstanding.) I mentioned the VOLMET at 10051, and I know there's another at 15034. The frequencies outside the SWBC bands are used for other purposes like marine and military, but 69xx is pretty free of that (excepting the MARS frequencies Chris mentions) and thus makes it less likely that you'll interfere with someone licensed who will notice and complain to the FCC. Confirmation and/or correction on this point is greatly appreciated, veteran DX'ers.

Good luck, and hope to hear your broadcast soon! Paranthetically yours, MDK2

[OgreVorbis]

After some research, it looks like the actual range is 6770-7000. It seems like this band aligns with the "land mobile" band right under 40 meters. Are there any specific stations to watch out for here (other than 6903, 6913 and 6915)?

How about the "land mobile" designations above and below the 20 meter band (13.87-14MHz and 14.35-14.99MHz)? Is there anything to watch for there? Apparently the 20m band is the most popular during the day?

I plan on operating AM. What is the normal audio bandwidth for AM on shortwave. Is it the same as the broadcast band (10khz)? Can I use whatever I want? My transmitter can go up to 50khz, so I'm deciding where to filter the audio.

I know these may seem like obvious questions to some of you, but I am not a ham, and I'm new to shortwave. (I do have all the equipment (spectrum analyzer) to make sure I'm not putting out any harmonics or spurs, though.)

Thanks for all the help!

[MDK2]

Check this out if you haven't already:

http://freeradiocafe.com/forum/index.php

Not that you can't get good answers here, but I believe this forum has a bit more emphasis on the practical aspects of unlicensed broadcasting.

[redhat]

After some research, it looks like the actual range is 6770-7000. It seems like this band aligns with the "land mobile" band right under 40 meters. Are there any specific stations to watch out for here (other than 6903, 6913 and 6915)?

How about the "land mobile" designations above and below the 20 meter band (13.87-14MHz and 14.35-14.99MHz)? Is there anything to watch for there? Apparently the 20m band is the most popular during the day?

I plan on operating AM. What is the normal audio bandwidth for AM on shortwave. Is it the same as the broadcast band (10khz)? Can I use whatever I want? My transmitter can go up to 50khz, so I'm deciding where to filter the audio.

I know these may seem like obvious questions to some of you, but I am not a ham, and I'm new to shortwave. (I do have all the equipment (spectrum analyzer) to make sure I'm not putting out any harmonics or spurs, though.)

Thanks for all the help!

Under ITU rules, 4.5 KHz is considered 'standard' audio bandwidth (but there is no license to appease so who cares ).  At the end of the day, most guys are listening with receivers that, SDR's withstanding, have limited audio bandwidth.  Wider audio also disperses transmitter power across a much large range of frequencies and will be perceived as 'more open' and 'less dense' than using narrower bandwidth audio, but there's no free lunch; coverage and listenability often suffers.  Wider receive bandwidth also lets more noise in, hampering reception of wide, weak signals.

In short, if your running DX and lots of power (over 250W carrier power) the North American NRSC-1 10 KHz modulation with pre-emphasis is a good way to go.  For lower powers, 3-5 KHz is usually best.  These are judgements made based on the airchecks I've received over the years from listeners, noting that most guys, even if wider bandwidth is available, will usually settle on 3-5 KHz.  So most of the time, that lovely twinkerbell percussion in your favourite disco number is most like going to be enjoyed only by yourself on your modulation monitor   SDR's are changing this, and as they become more prevalent, I would guess more people will be enjoying better audio from our stations.

[Pigmeat]

Above 6980 you start running into MARS nets again. There is some Mexican military traffic in that range, too.

Audio bandwidth? I ran a tad over 6 kHz wide. SW radios vary in their audio bandwidth on the wide setting, I figured 6khz at the top end with a sharp sloping cut above worked best for my set-up. All transmitters vary in the audio frequency range they can handle, you have to fool around a bit to get it honed in. The first few broadcasts are a shakedown cruise, no one gets it right the first time out and frankly, if you turn out like most of us you'll find yourself constantly fiddling with it throughout your career. Some folks consider it a chore, to me it's the fun part.

Have fun, it's not rocket science. 

[Josh]

40m is always open somewhere, and might as well consider 6995 to be 40m, local or dx. Also, the nearness to the HAM band allows one to oftentimes use HAM rigs as well as prefabbed antennas, both with little to no modification, for such illicit broadcasts.